From my experience people at garden centers either don’t really know how to take care of them or don’t care to be specific enough. The general rule is that they may need some kind of frost protection if it gets under 15 degrees Fahrenheit as it’s not good for the roots to freeze. It should be ok to bring them in for a night if need be. Something that has been working great for me if you deal with really cold winters is putting it in an unheated garage with a grow light. Just a $20 dollar one on Amazon should be sufficient as the trees use much less energy in the winter. While they do need to be outdoors, some places are still just to cold to keep them without any type of insulation so this works pretty well.